Great Basin Water Supply Outlook, March 1, 2020

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Brent.Bernard, Patrick Kormos
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Great Basin Summary






*Median of forecasts within each basin.


Bear Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Weber Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Six Creeks Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Utah Lake Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.


Bear Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume


Weber Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Weber
Oakley, Nr April-July73 84 97 82 119 135
Rockport Res, Wanship, Nr April-July72 83 101 77 127 149
Coalville, Nr April-July72 83 103 77 131 155
Chalk Ck
Coalville April-July12.4 16.8 23 56 32 51
Weber
Echo Reservoir, Echo, At April-July83 99 124 73 164 205
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July6.2 8.4 10.8 81 12.1 14.4
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July17.3 22 26 96 38 44
Weber
Gateway April-July139 191 245 75 315 395
Sf Ogden
Huntsville, Nr April-July38 47 55 98 65 82
Ogden
Pineview Reservoir, Ogden, Nr April-July66 77 101 89 137 154


Six Creeks Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Little Cottonwood Ck
Salt Lake City, Nr April-July32 34 37 97 43 48
Big Cottonwood Ck
Salt Lake City, Nr April-July29 32 35 97 42 49
Mill Ck
Salt Lake City, Nr April-July4.4 5.4 5.9 92 7.4 8.5
Dell Fk
Little Dell Reservoir April-July3.6 4.7 5.4 98 7.1 8.6
Lambs Ck
Salt Lake City, Nr April-July3.4 4.2 5.2 98 6.8 8.4
Parleys Ck
Salt Lake City, Nr April-July8.9 11.2 13.6 96 18.2 21
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.96 1.3 1.7 87 2 2.8
City Ck
Salt Lake City, Nr April-July4.9 5.5 6.5 84 7.5 9.2
S Willow Ck
Grantsville, Nr April-July2 2.2 2.5 81 3.1 3.8


Utah Lake Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Spanish Fork
Castilla, Nr April-July26 33 38 55 43 54
Provo
Woodland, Nr April-July76 81 91 91 107 119
Hailstone, Nr April-July81 87 98 89 114 129
Deer Ck Reservoir April-July88 97 106 83 132 147
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July16.4 19.2 21 68 27 32
West Canyon Ck
Cedar Fort, Nr April-July0.47 1 1.3 74 1.8 2.6
Salt Ck
Nephi Powerplant Div, Blo April-July2.9 3.8 5.4 65 7 9.9
Jordan
Utah Lake, Provo, Nr April-July168 189 215 66 280 315

Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).

Great Basin End of Month Reservoir Contents (kaf)

EOM
Contents		Percent
EOM
Average		Percent
Usable
Capacity		Last Year
EOM		Last Year
%Average		EOM
Average		Usable
Capacity
untitled Bear
Woodruff Narrows Reservoir, Woodruff, Nr 52.6 167 94 22.0 70 31.4 55.8
untitled Bear River
Bear Lake, Nr Lifton 1027.2 144 79 952.2 134 713.0 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 88 64 9.8 88 11.2 15.3
untitled Weber
Rockport Res, Wanship, Nr 49.5 142 90 29.5 85 34.8 55.2
Echo Reservoir, Echo, At 58.1 121 79 26.5 55 47.9 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 17.4 162 77 14.7 137 10.7 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 42.6 125 86 29.8 88 34.0 49.5
untitled Sf Ogden
Causey Reservoir 7.4 229 105 5.6 174 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 63.3 119 57 55.6 105 53.0 110.1
untitled Provo
Jordanelle Reservoir 265.1 110 83 193.8 80 241.2 320.3
Deer Ck Reservoir 145.0 127 97 120.5 106 113.9 149.7
untitled
14.7 -99 72 14.4 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 827.9 106 95 549.6 70 784.7 870.9
untitled
TOTAL 2565.9 123 85 2009.5 97 2079.1 3052.8

Precipitation Maps




Definitions

10% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 10% chance of being exceeded. Previously referred to as "Reasonable Maximum Forecast".

50% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 50% chance of being exceeded. Previously referred to as "Most Probable Forecast".

90% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 90% chance of being exceeded. Previously referred to as "Reasonable Minimum Forecast".

Acre-Foot (af): The volume equal to one acre covered one foot deep (43,560 cubic feet). See kaf below.

Average: The arithmetic mean. The sum of the values divided by the number of values. Values from 1981-2010 are used for this publication.

Categories: Much Above Average=Greater than 130%, Above Average=111-130%, Near Average=90-110%, Below Average=70-89%, Much Below Average=Less than 70%.

CBRFC: Colorado Basin River Forecast Center.

Forecast Period: The period from April 1 through July 31, unless otherwise noted.

kaf: Thousand Acre-Feet. See Acre-Foot above.

Inflow: The volume of water that flows into a reservoir or lake.

Median: The middle value of an ordered set of values. Half of the values are higher and half of the values are lower. When the set contains an even number of values the median is the average of the two middle numbers.

NOAA: National Oceanic and Atomospheric Administration.

NWS: National Weather Service.

Rounding Conventions:
RangeRound to
0-1.990.01
2.0-19.90.1
20-1991.0
200-9995.0
1000+3 significant digits


Streamflow: The volume of water that flows past a specific stream site.

Water Year: The 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends. Thus, the year ending September 30, 2008, is called the "2008 water year."


Additional Information

Water supply forecasts take into consideration present hydrometeorological conditions and use average basin temperatures and precipitation for the forecast period. As the forecast season progresses, a greater portion of the future hydrologic and climatic uncertainty becomes known and monthly forecasts become more accurate. For more information on the tools we use, consult Water Supply Forecasting Tools.

Volume forecasts represent adjusted flows; that is, observed flows with upstream water use taken into account. Adjusted flows will closely approximate natural or unimpaired flows. However, not all upstream diversions or impoundments are measured or quantifiable. For specific adjustments used with each forecast point, consult the Guide to Water Supply Forecasting.

The Water Supply Outlook is issued monthly January through May by the Colorado Basin River Forecast Center. It represents a coordinated effort between the National Weather Service, Natural Resources Conservation Service, Bureau of Reclamation, U.S. Geological Survey and local water district managers.

Note: Data used in this report are provisional and are subject to revision.

For more information, or to be included on the mailing list, please contact:

Colorado Basin River Forecast Center
2242 W North Temple
Salt Lake City, UT 84116
(801) 524-5130
www.cbrfc.noaa.gov


Hydrologist: Brent.Bernard, Patrick Kormos